I am working on building an Aquaponics system and in doing this you need to connect tanks of water together. You can of course use the normal bulkhead connectors that you need to glue/silicon and screw in place and I have several of these. There is also another type of bulkhead connector that is threaded with a nut and rubber washers to seal it, however I could not find those here in Switzerland in the sizes that I needed.

In looking for the bulkhead adapters I found that listed with them in many on-line stores was a product called a Uniseal® which is made by Injection Plastics MFG. CO. INC. They look like rubber, but they are made of DuPont Alcryn® and can handle 40psi

The installation looks quite straight forward and simple but I can tell you from first hand experience that it can be a bit of a struggle. Here are two YouTube videos that make it look easy however they are using a smaller diameter pipe than I was.

I throw in one more YouTube video in to show how Uniseals® make it possible to build some things that would be pretty much impossible. This is for a protein skimmer and they insert pipe into pipe with Uniseals®. In fact the picture for the video shows this. The audio for this video is a song and not narration. You may want to mute it due to the language used.

Now that you have an idea what a Uniseal® is and how it works, back to my story. I needed to connect two plastic tanks. One being my fish tank and one being my sump where the water would drain to once the fish tank gets full. The fish tank is a IBC. The sump is a plastic trunk for storing tools in your garden and such. The IBC has a very thin wall for the tank as the frame around it provides the needed rigidity to support the walls. The plastic trunk has much firmer walls.

Now before I go on I must add that the Uniseals® are engineered to work with US pipe sizes as you can see on The Uniseal Warehouse order form. The pipe I had to use is 50mm outside diameter. So after finding this little piece of information on the Shipwright Agencies Ltd website “Metric hole tolerances +2mm” I choose the U150 UNISEAL® – 1-1/2″(48mm). The holesaw that I used to make the holes in the tanks was the recommended metric size of 63.5mm.

I started with the pipe inside the IBC and pushed it out and into the sump tank. I found in my case this was the easiest as then the outside IBC frame held the tank wall in place while I pushed with all my might. The pipe needs to slope down between the two tanks, however I figured out very quickly that you can not install it that way. I did find that it the Uniseal will still seal even if the pipe is at an angle, but 15 degrees is the maximum. I had my wife stand in the sump and I pushed. I pushed the sump and my wife across the floor and the pipe did not go into the Uniseal®. I let my wife go and tried to figure out how to get the pipe in.

In the end what worked was to elevate the sump tank so that the pipe would go straight into the Uniseal®. I also used some wood to brace the tank so that it would not slide across the floor. I also used widow cleaner as recommended when inserting the pipe. I then sat down inside the IBC and pushed with one foot to push the pipe through the two Uniseals®. A constant firm pressure was what was needed. I found that twisting the pipe was not an help in my case as the Uniseal® and pipe rotated together instead of just the pipe turning.

To contrast this with the bulkhead adapters for the same size pipe I can with considerable effort twist the pipe through them and take it out if needed. With the Uniseals® It is going to have to stay where it is.

However, I am hopeful that with the effort it took to get them in that I will not have any leaks. Still need to test that.

Here are some pictures of my Uniseals® after they are installed. There is also a picture of on in a garbage can that I did as a test.